1. Field of the Invention
The present invention relates to a multihop relay wireless communication system. More particularly, the present invention relates to an apparatus and a method for determining a transmission time of a response signal in a multihop relay wireless communication system.
2. Description of the Related Art
In a wireless communication system, data transmitted and received over a radio channel can be distorted due to a channel condition and the received data may be subject to an error. Techniques for controlling and recovering the error include an Automatic Retransmission reQuest (ARQ) scheme and a Frame Error Check (FEC) scheme. According to the ARQ scheme, a receiving end requests retransmission of the compromised data to a transmitting end. According to the FEC scheme, the receiving end corrects the error caused by the corrupted data.
When the wireless communication system adopts the ARQ scheme, the receiving end can check for an error by decoding a received packet. When there is no error, the receiving end sends an ACKnowledge (ACK) signal to the transmitting end. When the data has an error, the receiving end sends a Non ACK (NACK) signal to the transmitting end. Receiving the ACK signal, the transmitting end sends a new packet. Receiving the NACK signal, the transmitting end retransmits the previous packet.
In response to the increasing demands for high-speed and high-capacity communications, adaptation of a multihop relay scheme is being considered. The multihop relay scheme ensures a good radio channel to a terminal traveling in a cell boundary or in a shadow area by using a relay station which relays signals between a base station and the terminal through the radio channel. That is, the multihop relay wireless communication system can provide a better radio channel between the base station and the terminal by relaying data transmitted and received between the base station and the terminal via the relay station.
Since the radio channel between the base station and the terminal includes a plurality of hops in the multihop relay scheme, signals are transmitted and received by multiple nodes. Accordingly, it is quite difficult to apply the ARQ scheme in the multihop relay wireless communication system. Therefore, what is needed is a method for executing the ARQ scheme by taking into account the relay station in the multihop relay wireless communication system.